The present invention relates to the improved structures of the push-button keys of the keyboard, which are characterized in that the coupling of the push-button keys and the upper housing panel is strengthened, and that the push-button keys can be pressed precisely without deviation, and further that letters, words, or Arabic numerals appeared on the surfaces of the push-button keys are disposed in such a manner that they do not become obscure after a prolonged usage thereof.
Referring to FIG. 1, the structure of the conventional keyboard keys of prior art is shown comprising an upper housing panel 1 with circular hole 11 arranged thereon. The circular hole 11 comprises two fastening hooks 12 arranged oppositely on the inner circumference thereof. A rubber elastic membrance 2 is disposed in the circular hole 11. A push-button key 3 comprises two hooking lugs 31 arranged oppositely on the undersides thereof. Located at the center of the underside of the push-button key 3 is a press column 32. In the process of assembling the push-button key 3 of keyboard, two hooking lugs 31 are allowed to engage with two fastening hooks 12 of the upper housing panel 1. The press column 32 is permitted to attach to the top portion of the rubber elastic membrance 2. The engagement of the two hooking lugs 31 and the two fastening hooks 12 is arranged in such a manner that there is a sufficient room for them to slide upwardly and downwardly. However, a secure coupling of the push-button key 3 and the upper housing panel 1 is always compromised by the fact that both hooking lugs 31 and fastening hooks 12 are not thick enough to sustain effectively the constant pressure exerting thereon. The thickness of both hooking lugs 31 and fastening hooks 12 must be limited because of the facts that there is a very little spare room located on both sides of the center line of the push-button key and that both hooking lugs 31 and fastening hooks 12 must be spaced apart from the inflated portion 21 of the rubber elastic membrane 2. The constructional design of the push-button key 3 is defective in that the push-button key 3 tends to move aside and inaccurately when pressed. As a result, the pressed push-button key 3 fails to exert a pressure directly on the upper portion of the rubber elastic membrance 2, thereby resulting in a poor contact which in turn may bring about a failure of data entry. In addition, both hooking lugs 31 and fastening hooks 12 are so constructed that they are susceptible to breakage when the push-button key 3 is pressed forcefully.